walls with Circular end

[NERDASORUS]

Hello

I want to create a wall type that always ends like this:

the radius is constant no matter what the length of the wall is, how to do that? (without the use of generic void families)

[L.Maas]

No voids or some separate family for the end piece

[barthbradley]

Snap a circular architectural column, that is the same material and diameter as the wall's thickness, to the end of the wall.  The column will automatically join to the wall - removing inner half of the column.  

[constantin.stroescu]

You can ,also,  use a Wall as Component Model in Place and if you make it a Group you can access it from Project Browser

[Ric_Weber]

A couple possible options I can see:

#1.  Create a thin wall type (e.g. just a sheetrock layer), perhaps one that is the same as the outside layer of your wall and place it at the end of the wall as a curved wall.

#2.  Did you not want to do a separate family as per @L.Maas reply?  If you're open to that, create a face hosted family that can have a variable height and width.

Otherwise your only other option would be to submit a Revit Idea on the Idea forum (if one doesn't already exist) and try to get some votes.  https://forums.autodesk.com/t5/revit-ideas/